Means for analyzing or synthesizing electric waves



Patented Oct. 27, 1925.

UNITED STATES PATENT OFFICE.

FRANK B. JEWETT, OF SHORT HILLS, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OIE' NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MEANS FOR ANALYZING OR SYN THESIZING ELECTRIC WAVES.

Application filed December 20, 1919. Serial No. 346,342.

T all whom, I? may concern Be it known that I, FRANK B. Jinwmr, a citizen of the United States, residing at Brantwood, Short Hills, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Means for Analyzing or Synthesizing Electric Waves, of which the following is a full, clear, concise, and exact description.

This invention relates to means and methods for analyzing or synthesizing electric waves.

An object of this invention is to provide a convenient arrangement for combining into a composite wave form a plurality of harmonically varying alternating currents adjusted with respect to each other as to frequency, phase, and amplitude relations. Another object of this invention is to provide means for analyzing a composite wave form into a desired number of elementary waves. A further object is to do this electrically, with the numerous advantages which obtain in an electrical system, such as flexibility of adjustment, compactness and freedom yfrom variations in the physical constants of the metal springs and other parts constituting the usual mechanical analyzer. Still a further object is to devise an electrical system in which amplification of weak power is feasible and in which the power used in the moving recording parts does not react on the harmonic oscillations to be combined.

The process involved in employing this invention as an anlyzer of electric waves will be better understood by reference to an article by Michelson and Stratton in the American Journal of Science of 1898, vol. 5, pages 1 to 13, in which the operation of a mechanical harmonic analyzer is described in detail.

The arrangement provided in accordance with the present invention employs one or more vacuum tube amplifiers of the type now well known in the art, wherein the electron discharge between two electrodes may be varied in accordance with potential variations applied to a control electrode adjacent the electron discharge path. In one form of this invention a plurality of these vacuum tube amplifiers are employed so connected as to have a common output circuit for all the tubes, these tubes being connected in series or parallel. If, now, a harmonically varying potential of a predetermined phase, amplitude, and frequency, is impressed on the control electrode of each tube, there results in the common output circuit a composite wave formed by the combination of the individual alternating current waves impressed on the various control electrodes. The common output circuit may contain suitable apparatus, such as an oscillograph, for recording purposes.

One way the elementary alternating current waves may be produced is by means of a multiple unit potentiometer located in the input circuits of the tubes, the contacts of the potentiometer being under the control of a suitable driving mechanism, which is capable of being adjusted to produce the phase and amplitude variations desired. Or, if desired, the amplitude of the waves may be varied by adjusting the I R drop in each potentiometer wire so that only the phase relations of the waves need be adjusted by means of the driving mechanism.

This invention will be better understood by reference to the following detailed description taken in connection with the accompanying drawings, in which Fig. 1 represents one form of this invention in which a separate vacuum tube amplifier is ernployed for each elementary wave. Fig. 2 is a modification of Fig. 1 in which vacuum tubes are employed each having a plurality of control electrodes; and Fig. 3 illustrates how a lsingle vacuum tube may be employed for producing a composite wave by the combination of a plurality of elementary waves imbpressed on the control electrodes of the tu e.

Referring to Fig. 1, the harmonic analyzer comprises a plurality of vacuum tube amplifiers 5, 6, 7 and 8 which contain respectively cathodes 9, 10, 11 and 12, anodes 13, 14, 15 and 16 and control electrodes 17, 18, 19 and 20. Heating current for the cathodes is supplied from a battery 21. The cathodes 100 and the anodes of the tubes are connected to a common output circuit which includes a source of voltage 22 and the suspension element 23 of an oscillograph, or the heating mechanism of any other suitable recording 105 device.

In order to generate the various alternating current potentials which are to be iIn pressed on the control electrodes of the amplifiers, a multiple unit potentiometer is pro- 110 vided which comprises a plurality of potentiometer wires 26, 27, 28 and 29. Intermediate points of these potentiometer wires are connected together by means of a wire 30. Battery 81 supplies currents for that part of each potentiometer wire which is connected between leads 30 and 32, while battery 33 supplies current to that part of each potentiometer wire which is connected between leads 30 and 34. A variable resistance 35 is provided for the indivdual variation of the current owing through that part of potentiometer wire 26 which is located between leads 30 and 32. A second variable resistance 36 is provided for allowing the individual adjustment of the current flowing in that part of potentiometer wire 26 which is located between leads 30 and 34. In a similar manner other resistances are provided, as shown, for varying the current in each half of potentiometer wires 27, 28 and 29. Contact 40 is given a harmonically varying movement along wire 26 by means of crank arm 41 which is attached to a crank wheel 42 driven by a gear 48 located on the rotatable shaft 44. Contact 45 for wire 27 is driven by means of a crank arm 52 which is attached at one end to crank wheel 46, which is driven by a gear 47 located on the rotatable shaft 44. In a similar manner contacts 48 and 49 may be driven by suitable gearing mechanism driven by shaft 44. In the preferred form of this invention, shaft 44 is driven by motor 50 or other source of power, which is employed for furnishing the driving power for the oscillograph 51.

The operation of this invention will be understood by noting the various elements that determine the potential of each control electrode of the vacuum tube an'ipliliers. The variation in potential between control electrode 17 and cathode 9 is determined by that part of potentiometer wire 26 which is located between contact 40 and lead 30. The variation in potential between control electrode 18 and cathode 10 is determined by the I R drop in that part of wire 27 located between contact 45 and lead 30. The variation in potential between control electrode 19 and cathode 1l is determined by the I R drop in that part of wire 28 located between contact 48 and lead 30. Similarly, the variation in the potential of control electrode 20 is determined by that part of potentiometer 29 located between contact 49 and lead 30. It follows, therefore, when shaft 44 is rotated, that a harmonic movement is given to each of the potentiometer contacts and consequently a harmonically varying potenial is applied to each control electrode of the tubes. Individual adjustment of the static potentials of the grids is secured by means of batteries 55, 57, 58 and 59. Battery 56 provides for the common adjustment cuit ofthe tubes which includes the oscillograph suspension 23 will contain a composite wave form resulting from the combination of the elementary harmonically varying potentials applied to the control electrodes of the tubes. The frequency of each of the elementary alternating current potentials will be determined by the number of cycles performed by potentiometer contacts in unit time and may therefore be adjusted by varyinfr the gearing mechanism located between the shaft 44 and the respective arms for the contacts. In general, the frequencies of the various alternating current potentials should have values which bear to each other the ratios 1, 2, 3, 4, 5, 6, etc. The amplitude of each elementary harmonically varying alternating current potential may be determined by either adjusting the variable resistances connected in series with each potentiometer wire or by adjusting the distance between the center of each crank wheel and the point at which the crank arm is fastened so as to make each potentiometer contact move over more or less of its potentiometer wire as required. 'lhe phase difference between the elementary alternating potentials may be readily determined by adjusting the gearing mechanism for the potentiometer contacts so that the relative positions of the contacts in their cycles of operations bear the same relation to each other as it is desired to have between the phase values of the alternating current lwaves or by other well known expedients such as changing the position of the associated crank as shown in Fig. 1.

From the above description it is apparent that the various elementary alternating current potentials may be so adjusted as to phase frequency and amplitude values that there results in the common output circuit of the tubes a composite wave of any form desired. There will also be no reaction between the output circuit and the circuits of the individual sources of electric waves, due to the fact that the vacuum tubes disclosed are of the uni-directional type, thereby insuring a high degree in accuracy in the co1nbination of the simple harmonic waves. It is obvious that the composite wave form may be made up of as many elementary waves as is desired by employing additional potentiometer wires and additional vacuum tube `amplifiers.

In the form of this invention disclosed in the drawings, it is desirable that the complex wave formed in the output circuit of the tube or tubes should result from the simple combination of the various components without any distortion or intermodulation taking place. Modulation may be avoided by having the vacuum tubes operate on the straight part of their characteristic curves. It is within the scope of this of these potentials. The common output cirinvention, however, to employ the circuit llO arrangement of this invention for such uses as would make modulation desirable.

In the modification of F ig. 1 shown in Fig. 2, vacuum tube amplifiers are employed, each having a plurality of control electrodes. Since an elementary alternating current potential may be applied to each control electrode, it follows that this system, as compared to that of Fig. l, requires a smaller number of tubes for the production of a composite wave resultingr from the combination of a given number of elementary waves. Tube 60 comprises a cathode 61, an anode 62 and a plurality of control electrodes 63, one of which is shown connected to contact 64 of potentiometer wire 65. Tube 66 comprises an anode 67, a cathode 68 and a plurality of contr-ol electrodes 69, one of the control electrodes being connected to potentiometer contact 70,v another one being connected to potentiometer contact 71. Con- 4tacts 64, 70 and 71 may be driven by mechanism similar to that shown in Fig. 1. The potentiometer arranged for Fig. 2 is slightly different from Fig. 1 in this respect, that in Fig. 1 there are two circuits each comprising a part of a potentiometer wire that require adjustment for each alternating potential desired; in Fig. 2 there is only one circuit to be adjusted for each frequency. However, in Fig. 2 it will be necessary to have the batteries, such as 75, not only fix the grid potentials so as to cause the tubes to work on the desired part of their characteristic curves, but also to compensate for the drop of potential in that part of each potentiometer wire located between wire 7 3 and the central point of the path of each potentiometer contact. As shown in the drawing, the cathodes and anodes of the tubes 60 and 66 maybe connected in circuit with a suitable recording device 77.

Fig. 3 shows how a single vacuum tube amplifier may be employed in producing a composite wave from a plurality of elementary waves. In this arrangement, an individual battery is provided for each potentiometer wire. Thus wire is connected in series with battery 81, wire 82 is connected in series wth battery 83, wire 84 is connected to a battery 85, and so on. Each of the potentiometer contacts 87, 88, 89 and 90 may be given a harmonically varying motion by driving mechanism similar to that shown in Fig. 1. The control electrode 91 of tube 92 will have impressed on it a harmonically varying potential of certain frequency, phase, and amplitude values due to the motion of contact 87. The control electrode 91 will also have impressed on it a harmonically varying potential of certain characteristics due to the motion of contact 88. Similarly, other elementary harmonically varying potentials will be im* pressed on the control electrode 91 due to the motion of contacts 89, 90, and any others that may be employed. There will result in the output circuit of tube 92 a composite wave form resulting from the combination of various elementary potentials applied to electrode 91.

It is to be understood that this invention is not limited to the particular forms above described, but that it may be variously modified without departing in any wise from the spirit of the invention as described in the appended claims.

lVhat is claimed is:

1. In a wave producing system, means to produce a space discharge current, control circuits for varying said space discharge current in accordance with impressed waves, means to impress on said contro-l circuits simultaneously a plurality of waves of substantially sinusoidal wave form and each of a different frequency, means to control the phase, amplitude and frequency of the various impressed waves to produce space current variations representing a complex wave of given characteristics, and means for indicating said complex current wave.

2. In an electric system, a plurality of/ sources of electric waves substantially elementary in form, means comprising an elec'- tron discharge device for combining said elementary wave forms into a complex wave form, and recording means associated with said electron discharge device.

3. In an electric system, a plurality of sources of electric waves each of substantially a single frequency, means comprising a vacuum tube fo-r combining said single frequency waves into a complex wave, and recording means associated with the output circuit of said tube.

4. In au electric system, a plurality of sources of electric waves each of substantially a single elementary frequency, a plurality of vacuum tubes each having a cathode, an anode and a. control electrode, connections for impressing on each of said control electrodes one of said elementary frequencies, a common output circuit for said tubes, and a receiving device associated with said output circuit for the complex wave resulting in said output circuit from the combination of said elementary frequencies.

5. The combination of mechanism for gen erating a plurality of electricc waves each of substantially an elementary frequency. a plurality of vacuum tubes cach having a cathode, an anode and a control electrode. connections for impressing on cach of said control electrodes one of said simple frequencies, and a common output circuit for said tubes comprising an oscillograph suspension.

6. The combination of mechanism for generating a plurality of electric waves each of` substantially a single frequency, a plurality of vacuum tubes each having a cathode, an anode and a control electrode, connections for impressing on each of said control electrodes one of said simple frequencies, an oscillograph associated with said tubes, and a common means for driving said mechanism and the rotating parts of said oscillograph.

7. The combination of a plurality of vacuum tubes each having an input circuit, a common output circuit for said tubes, a receiving device associated With said output circuit, a variable resista-nce in the input circuit of each of said tubes, and mechanism for substantially harmonically varying the value of each of said resistances.

8. The combination of a vacuum tube, means for supplying space current to said tube, and means for simultaneously varying said space current in accordance with a plurality of liarmonically varying potentials, said second means comprising a plurality of variable resistances and mechanism for simultaneously varying in a substantially harmonic manner the value of said resistances.

9. The combination of a plurality of vacuum tubes having a common output circuit and each having an input circuit, a common source of direct current potential for said input circuits, and an individual source of direct current potential for each of said input circuits.

10. The combination of an electron discharge circuit having a plurality of input electrodes, a plurality of sources each of substantially single frequency, means for varying the potential of each of said input electrodes, in accordance With a single frequency derived from one of said sources, an output circuit for said electron discharge circuit, and means for indicating the complex current in said output circuit.

11. In combination, a vacuum tube, a space current path in said tube, means for controlling said space current, an indicating device responsive to variations in said space current, and unitary means for varying the effect of said controlling means for controlling said indicating device in a manner supplementary to its response to said space current.

12. In combination, a vacuum tube having a control electrode, a recording device responsive to a condition of said tube and having a movable member, and unitary means for varying the potential of said control electrode and for moving said movable member, the energy for moving said movable member being supplied irrespective of variations in the potential of said control electrode.

13. In combination, a vacuum tube having an anode, a cathode and a control electrode, a variable impedance for controlling the potential difference between said control electrode and said cathode, an indicating device responsive to a condition of said tube, and unitary means foi` varying the effective valueof said impedance for controlling said indicating device in a manner supplementary to its response to said space current.

14. In combination, a vacuum tube having an anode, a cathode and a control electrode, an adiustable resistance for varying the potential difference betiveen said cathode and said control electrode, a curve tracer, and unitary means for varying the effective value of said resistance and for operating said tracer.

15. In combination, a vacuum tube having Aan anode, a cathode and a control electrode, an adjustable resistance for varying the po'- tential difference between two of said electrodes, a curve tracer, a motor, means operated by said motor for varying said resistance, and means operated by said motor for operating said curve tracer.

16. In an electric system, a plurality of sources of electric Waves substantially elementary in form, means comprising an electron discharge device for combining said elementary wave forms into a complex Wave form, and indicating means associated With said device, said device being adjusted to operate with a substantially linear relation between its input voltage and output current.

17. In combination, a plurality of vacuum tubes, each having a control electrode, an adjustable impedance element for varying the potential of each of said control electrodes, and unitary means for varying said impedances.

18. In combination, a vacuum tube having an input circuit and an output circuit, an indicating device associated With said output circuit, an impedance in said input circuit, and a source of povver for cyclically varying the value of said impedance.

19. In combination, a vacuum tube having an input circuit and an output circuit, an indicating device associated With said output circuit, a potentiometer Wire in said input circuit, a motor, and mechanism driven by said motor for varying the effective value of said potentiometer Wire.

20. In combination, a vacuum tube having a control electrode, a source of voltage, an impedance element in circuit with said source, a movable contact on said element, connections from said element including said movable contact for determining the direct current potential of said control electrode by the position of said movable contact, and motor driven mechanism for varying the position of said movable contact.

21. In combination, means for generating a plurality of electric Waves, each of substantially an elementary frequency, a plurality of vacuum tubes, each.- having an anode, a cathode and a control electrode, conloo nections for impressing on each of said control electrodes one of said simple frequencies, and a common output circuit for said tubes.

22. In combination, a plurality of means for generating harmonic Waves, each of substantially an elementary frequency, a common output line for said means, and means comprising a vacuum tube of tlie uni-directional type located between said line and said means for preventing said output line from reacting on the said means.

23. In combination, an electron discharge circuit having a plurality of control electrodes, a plurality of sources each of substantially a single frequency and means for impressing a diiierent simple harmonic potentialA derived from one of said sources upon each of said control electrodes.

In Witness whereof, I hereunto subscribe 20 my name this 16th day of December A. D., 1919.

FRANK B. JEVETT. 

